Ion producing mechanism



Sept, 9, 1958 w. M. BROBECK 2,351,609

'ION PRODUCING MECHANISM (ARC EXTERNAL TO BLOCK) Filed Jan. 16, 1946 2 Sheets-Sheet 1 BY W4 M p 1958 w. M. BROBECK 2,851,609

ION PRODUCING MECHANISM (ARC EXTERNAL TO BLOCK) Filed Jan. 16, 1946 2 Sheets-Sheet 2 INVENTOR. h/////0/77 M Broeck BY WM HQN PRODUCHNG MECHANISM (ARC EXTERNAL T BLOCK) William M. Brubeck, Berkeley, Calif., assignor to the United States of America as represented by the United States Atomic Energy Commission Application January 16, 1946, Serial No. 641,614

Claims. (Cl. 250-413) The invention is concerned with ion producing mechanisms especially of the type referred to as calutrons in which a material to be ionized is formed into a gas or vapor and is passed through or adjacent to an electric arc wherein a proportion of the vapor or gas is ionized. This type of structure is disclosed and described in detail in United States Patent No. 2,709,222, issued May 24, 1955, to Ernest 0. Lawrence, and an embodiment of the invention to which the present invention is especially germane is especially disclosed in Figures 3 to 5 in the identified patent.

In the operation of a calutron, it is especially desirable to increase the amount of ionization elfectuated by the arc as much as possible, to maintain the are as nearly uniform as possible in point of time, in arc location, and along the arc length. it is also highly desirable to withdraw as many ions as possible from the arc and this is normally considered to involve the amount of arc surface exposed to a withdrawing influence such as the action of an accelerating electrode.

It is therefore an object of the invention to provide means for improving the ionizing action of an arc in a calutron.

Another object of the invention is to improve the steadiness of operation and the uniformity or the consistency of a calutron arc.

Still additional object of the invention is to provide additional available area of an are for the withdrawal of ions therefrom.

Another object of the invention is in general to improve the operation of an ionizing arc.

A still further object of the invention is in general to improve the operation of a calutron.

Other objects together with the foregoing are attained in the embodiment of the invention described hereinafter and shown in the accompanying drawings, in which:

Figure 1 is a fragmentary view of a calutron, particularly the source section thereof, with portions of the structure being broken away principally on a vertical, median plane to disclose the interior construction of the unit and with other portions being broken away to reduce the size of the figure.

Fig. 2 is a fragmentary view of the source section disclosed in Pig. 1, the drawing being in isometric perspective with portions of the structure being broken away to disclose the interior arrangement.

Fig. 3 is a cross section of the structure shown in Fig. 2, the plane of section being indicated by the line 33 of Fig. 2.

Fig. 4 is a plan of the structure shown in Fig. 2, a portion of a top plate being broken away to disclose the structure therebelow.

While a calutron is described in considerable detail in the above-identified patent of Lawrence, a brief review of that structure will suffice for an understanding of the present development and is given in connection with Fig. 1.

In a calutron there is provided a volume 6 permeated by a uniform or homogeneous magnetic field established ai -51f between the upper pole 7 and the lower pole 8 of an electromagnet. Disposed between the poles 7 and 8 and situated within the magnetic field is a tank or vessel 9 enclosing a chamber lll connected to suitable pumping mechanism such as a diffusion pump (not shown) effective normally to evacuate the chamber 11 to a pressure of approximately 10* mm. of mercury. The tank 9 includes a top wall 12, a bottom wall 13, and a face plate 14.

Secured removably to the face plate is an insulator 16 serving also as a support for a mounting and adjusting mechanism 17 not described in detail herein as its detailed functioning is not of consequence in connection with the present invention. The structure 17, however, acts as a support for a mounting stem 18 of a source block 1?. A number of conductors 21 and leads 22 included in the structure 17 pass with vacuum tightness from the atmosphere into the interior of the chamber 11. The stem 13 is preferably related to the source block 19 by a terminal flange 26 and suitable fastenings 27 so that while some thermal insulation is afforded there is nevertheless good electrical contact.

The source block 19 is at its inner end provided with a heater cavity 28 closed by a disk 29 at its upper end and receiving through its lower end an electric coil heater 31 mounted on an insulating core 32. The heater coil is connected to a pair of leads 33 and 34 one being joined to one end of the conductor 22 and the other being connected to the block or flange 26. Upon the imposition of a suitable potential difference between the conductors 18 and 22 the heater 31 is effective to increase the temperature of the block 19. The source block preferably is of metal so that heat from the coil 31 is generally conducted in a uniform fashion to a charge cavity 36 formed within the block 19. The charge cavity extends nearly through the under side of the block and entirely through the top face 37 thereof.

Establishing communication between the cavity 36 and the exterior face 38 of the block 19 is a gas passage 39 defined by a pair of parallel planar walls 41 and 42 so that the passage is a straight one extending from within the block to the outside thereof and thus merging not only with the face 38 but also with the adjacent face 37. When charge material is placed in the cavity 36 it is heated and evolves gas or vapor that travels from the cavity 36 rather uniformly through the passage 39 to the exterior of the block.

To close the cavity 36 and a part of the passage 39 there is provided on the face 37 in abutment therewith a plate 53 fastened to the block 19 by suitable screws 4% and effective to seal one end of the cavity and one end of the passage. The plate 43 preferably extends beyond the face 38 and overhangs the edge of the block in. The plate is provided, in registry with the passage 39, with an aperture 46 preferably symmetrically disposed with respect to the passage.

More particularly, in accordance with the current invention, there is disposed above the cover plate 43 and in partial registry with the passageway 39, a filament 47 serving as a cathode for the production of an arc. The filament not only overlies the passageway 39 but extends considerably beyond the terminus of the passageway, even beyond the face 38 of the source block 19 and is then provided with a reverse bend 43. The ends of the filament 47 are thus parallel and are both available to be held in a pair of grips 49 and 50, respectively, at the ends of supporting conductors 51 and 52, in turn joined to the leads 21. One of the grips, for example 49, is extended to provide a plate 53 overlying and even extending beyond the plate 43.

In accordance with the present invention, the aperture 46 extending through the plate and underlying the de sired emitting portion of the filament l7 overlies not only Patented Sept. 9, 1958 a large part of the passageway 39 but also, as particularly shown in Fig. 3, overlies in part an area or volume in front of the face 33 of the block. The filament 47 and the block 19 are included by means of a power supply 55 (illustrated schematically) in an electric arc circuit efiective to cause an arc to strike between the filament 47 and the block 19. The main body of the arc is of elongated form passing through the aperture 46 and extending partly within and partly without but nevertheless along the length of the passageway 39 and encountering the lower face 57 of the block 19 as well as the face 38 thereof as an anode.

In accordance with this arrangement, when the heater 31 is energized, charge material 58 within the charge chamber 36 is formed into a vapor of gas and discharges from the chamber 36 through the passageway 39. The gas encounters and must pass through or adjacent to not only the arc existing in part within the channel 39 but also that portion of the are which is exterior to or beyond the face 33. Thus the likelihood of ionization occurrring is greatly increased. Additionally, since the arc in part is not confined by the passageway 39, a large surface thereof is exposed to the action of any withdrawing mechanism such as an accelerating electrode so that the quantity of ions withdrawn from the arc is increased.

Pursuant to this invention, therefore, there is provided a means for producing a stable are from which a copious supply of ions can readily be withdrawn, that is uniform along its length and stable in operation. The operation of the ionizing mechanism and of the calutron in general is considerably improved.

What is claimed is:

1. In an ion producing mechanism for a calutron having a magnetic field, the combination comprising a source block having a gas ionizing passage extending through a first wall thereof being disposed parallel to said magnetic field and a communicating opening extending through a second wall thereof being disposed transversely to said first wall, a filament disposed parallel to said second wall in alignment with said opening and having a portion extending beyond the external face of said first wall, means connected between said filament and said block for providing an electric arc circuit, means for passing an ionizable gas through said passage, and a filament shield disposed between said filament and said block, said shield having an aperture therein disposed to limit ionizing electron emission of said filament to said passage and a limited area external thereof.

2. In an ion producing mechanism for a calutron having a magnetic field, the combination comprising a source block having a gas ionizing passage extending through a first wall thereof being disposed parallel to said magnetic field and a communicating opening through a second wall thereof being disposed transversely to said first wall, a filament disposed transversely to said first wall in parallel and aligned relation with said opening and having a portion extending beyond the external face of said first wall, means for passing an ionizable gas through said passage, and means connected to said filament and said block for establishing an electric arc whereby an arc plasma is formed within said passage and extending beyond the external face of said first wall.

3. In an ion producing mechanism for a calutron having a magnetic field, the combination comprising a source block having an elongated gas ionizing passage extending through a first wall thereof being disposed parallel to said magnetic field and a communicating opening extending through a second wall thereof being disposed transversely to said first wall, a filament disposed parallel to said second wall and spaced therefrom, said filament having a straight, elongated, and emissive portion parallel to and aligned with said opening with one end extended beyond the external face of said first wall, means connected between said filament and said block for providing an electric arc circuit, means for passing an ionizable gas through said passage, and a filament shield disposed between said filament and said block, said shield having an aperture therein disposed to limit the ionizing electron emission extending from the elongated portion of said filament to a portion of said passage and a limited area immediately beyond.

4. The combination of claim 3 wherein the filament shield is further characterized as removably secured to said second wall and the aperture thereof is disposed in part over said passage and in part over a limited area external of said passage.

5. The combination of claim 3 wherein the gas ionizing passage is characterized as being defined by a pair of parallel planar walls spaced apart by an amount substantially less than the elongation thereof.

Bleakney Nov. 12,4940 West Sept. 16, 1947 

